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Cross‐sectional study of histopathology and piscine orthoreovirus during a marine production cycle of farmed Atlantic salmon ( Salmo salar L.) in British Columbia, Canada
Author(s) -
Marty Gary D.,
Bidulka Julie,
Joseph Tomy
Publication year - 2020
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/jfd.13210
Subject(s) - salmo , hatchery , biology , histopathology , cohort , fishery , fish hatchery , fish farming , veterinary medicine , aquaculture , fish <actinopterygii> , zoology , pathology , medicine
Two cohorts of farmed Atlantic salmon, Salmo salar L., in British Columbia, Canada, were sampled for histopathology (nine organs) and piscine orthoreovirus (PRV‐1) PCR after seawater entry at 2, 4, 6, 8, 10, 13, 16 and 19 months (20 fish per cohort per date). One cohort—from a PRV+ hatchery—remained PRV+ throughout the study (sample prevalence 80%–100%). In an adjacent pen, the other cohort—from a PRV− hatchery—was 0% PRV+ at 78 days, 30% PRV+ at 128 days and ≥95% PRV+ thereafter. Among sample cohorts that were ≥80% PRV+, median Ct values were nominally less among fish sourced from the PRV− hatchery (28.7–33.3) than the PRV+ hatchery (30.8–35.2). No microscopic lesions were associated with PRV Ct value (minimum = 25.6). About 3% of fish in both cohorts had moderate inflammatory heart lesions; among these fish, only one had skeletal muscle inflammation (mild), and PRV Ct values were similar to unaffected cohorts sampled the same day. Also, among 16 moribund or freshly dead fish sampled opportunistically during the study, 14 were PRV+, and none had significant inflammatory heart lesions. These data support the hypothesis that British Columbia PRV‐1 does not contribute to mortality.